This invention relates to semiconductor devices, and more specifically relates to a novel contact structure for such devices.
Semiconductor devices used for higher current ratings (power devices which are generally those which handle in excess of one watt of power) have various types of contact structures which help to remove heat from the semiconductor die to areas external of the die or its package.
One structure which is very efficient for that purpose is the xe2x80x9cCopper Strapxe2x80x9d package of International Rectifier Corporation in which the top electrode, for example, the source electrode of a Power MOSFET, is contacted by a thick copper contact which efficiently extracts heat from the die, and also serves as a source contact for the device. This device is shown in U.S. Pat. No. 6,040,626, the disclosure of which is incorporated by reference herein.
Another International Rectifier Corporation patent, U.S. Pat. No. 6,396,127, discloses a semiconductor package including a semiconductor power MOSFET die having a bottom surface defining a drain connection and a top surface on which a first metalized region defining a source and a second metalized region defining a gate are disposed, the bottom surface being coupled to a first terminal; a copper plate coupled to and spanning a substantial part of the first metalized region defining the source connection, the copper plate including at least one chamfered edge extending upward and away from the first metalized region; and at least one beam portion being sized and shaped to couple the copper plate portion to the at least one second terminal such that it is electrically coupled to the source.
Another device, known as a xe2x80x9cDirect FETxe2x80x9d device, also made by International Rectifier Corporation, employs a flip chip type die, for example, a MOSFET with source and gate balls on one surface of the die. The back surface of the die (the drain electrode) receives a cup-shaped metal drain contact which has a flange telescoped over the edge of the die, which flange terminates in the plane of the source and gate balls. Thus, the device is easily surface mounted on a printed circuit board or the like. Such a device is shown in copending application Ser. No. 09/819,774, filed Mar. 28, 2001 entitled CHIP SCALE SURFACE MOUNTED DEVICE AND PROCESS OF MANUFACTURE in the names of Martin Standing and Hazel Deborah Schofield, pending; the disclosure of which is incorporated by reference herein.
It would be desirable to retain or improve the thermal characteristics of existing devices while also simplifying the manufacture process.
The present invention relates to a novel bump strap package which has a flip-chip die with bottom source and gate bumps (for a MOSFET for example) and having a top U-shaped stress-relieving copper drain contact strap with connection ear portions at its opposite ends. A second semiconductor die (for example, an IC for the first die) can be mounted on the top surface of the drain strap.